U.S. patent number 9,829,552 [Application Number 14/243,402] was granted by the patent office on 2017-11-28 for transmission arrangement for a tomograph.
This patent grant is currently assigned to Siemens Aktiegesellschaft. The grantee listed for this patent is Andre Albsmeier, Sebastian Martius, Markus Vester. Invention is credited to Andre Albsmeier, Sebastian Martius, Markus Vester.
United States Patent |
9,829,552 |
Albsmeier , et al. |
November 28, 2017 |
Transmission arrangement for a tomograph
Abstract
A transmission arrangement for a tomograph, such as magnetic
resonance tomography, is provided for wireless energy supply of a
local coil system. The transmission arrangement includes at least
one first region having at least one first antenna element. The
transmission arrangement further includes at least one second
region having at least one second antenna element. The at least one
first region and the at least one second region are connected to
one another via at least one rejector circuit.
Inventors: |
Albsmeier; Andre (Munchen,
DE), Martius; Sebastian (Forchheim, DE),
Vester; Markus (Nurnberg, DE) |
Applicant: |
Name |
City |
State |
Country |
Type |
Albsmeier; Andre
Martius; Sebastian
Vester; Markus |
Munchen
Forchheim
Nurnberg |
N/A
N/A
N/A |
DE
DE
DE |
|
|
Assignee: |
Siemens Aktiegesellschaft
(Munich, DE)
|
Family
ID: |
51567509 |
Appl.
No.: |
14/243,402 |
Filed: |
April 2, 2014 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20140300361 A1 |
Oct 9, 2014 |
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Foreign Application Priority Data
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Apr 3, 2013 [DE] |
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10 2013 205 817 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01R
33/34046 (20130101); G01R 33/34092 (20130101); G01R
33/3692 (20130101); G01R 33/34076 (20130101); G01R
33/288 (20130101); G01R 33/481 (20130101) |
Current International
Class: |
G01R
33/36 (20060101); G01R 33/34 (20060101); G01R
33/28 (20060101); G01R 33/48 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1393699 |
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Jan 2003 |
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CN |
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1868406 |
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Nov 2006 |
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CN |
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69925193 |
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Feb 2006 |
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DE |
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102006052217 |
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May 2008 |
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DE |
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102011076918 |
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Dec 2012 |
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DE |
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Other References
Arnulf Oppelt, "Imaging Systems for Medical Diagnostics", Publicis
Corporate Publishing, 2005, ISBN 3-89578-226-2 [table of contents].
cited by applicant .
German Search Report in corresponding German Patent Application No.
DE 10 2013 205 817.9 with translation, dated Dec. 4, 2013, 10
pages. cited by applicant .
Chinese Office Action for related Chinese Application No.
201410132482.6 dated Sep. 5, 2017. cited by applicant.
|
Primary Examiner: Curran; Gregory H
Attorney, Agent or Firm: Lempia Summerfield Katz LLC
Claims
The invention claimed is:
1. A transmission arrangement for a tomograph, the transmission
arrangement comprising: a first region having at least one first
antenna element, wherein the first region is configured to operate
at a first operating frequency; and a second region having at least
one second antenna element, wherein the second region is configured
to operate at a second operating frequency; wherein the first
region and the second region are connected to one another via a
rejector circuit, wherein the rejector circuit is configured to
reject the first operating frequency.
2. The transmission arrangement of claim 1, wherein the first
operating frequency is an excitation frequency for exciting a
nuclear spin.
3. The transmission arrangement of claim 1, wherein the second
operating frequency is an energy input frequency to supply a local
coil system with energy.
4. The transmission arrangement of claim 1, wherein: the first
region has a plurality of first antenna elements connected to one
another via tuning devices; the tuning devices have an impedance
for the second operating frequency; a pair of second regions is
adjacent to the first region on each side of the first region such
that second antenna elements of each second region are connected to
the second antenna elements of the other second region via a first
antenna element of the first region; and the rejector circuit is
transmissive at the second operating frequency.
5. The transmission arrangement of claim 4, wherein: the first
region is designed as a first body coil arrangement having first
antenna elements arranged in parallel, with neighboring first
antenna elements being connected to one another by at least two
tuning devices; the second region comprises two second body coil
arrangements, each second body coil arrangement having second
antenna elements arranged in parallel; neighboring second antenna
elements of the second region are connected to one another by a
connecting element; and neighboring second antenna elements of the
second region are connected to one another via at least two of the
first antenna elements of the first region.
6. The transmission arrangement of claim 5, wherein: the
transmission arrangement has a cylindrical basic shape; and the two
second regions are adjacent to the first region at end faces.
7. The transmission arrangement of claim 5, wherein the connecting
element is connected to the second antenna elements via rejector
circuits for the first operating frequency.
8. The transmission arrangement of claim 5, wherein the connecting
element between neighboring second antenna elements has a rejector
circuit for the first operating frequency.
9. The transmission arrangement of claim 1, further comprising a
plurality of input points, the plurality of input points
comprising: a first input point at the second region; a second
input point at the first region; a third input point at the second
region; and a fourth input point at the first region wherein the
first and third input points are offset by 90.degree. with respect
to one another.
10. The transmission arrangement of claim 9, wherein: the first
input point and the second input point are opposite one another;
and the third input point and the fourth input point are opposite
one another.
11. The transmission arrangement of claim 1, wherein the rejector
circuit is configured as a parallel resonant circuit.
12. The transmission arrangement of claim 11, wherein the rejector
circuit is provided for bridging a detuning circuit on the first
region.
13. The transmission arrangement of claim 2, wherein: the first
region has a plurality of first antenna elements connected to one
another via tuning devices; the tuning devices have an impedance
for the second operating frequency; a pair of second regions is
adjacent to the first region on each side of the first region such
that second antenna elements of each second region are connected to
the second antenna elements of the other second region via a first
antenna element of the first region; and the rejector circuit is
transmissive at the second operating frequency.
14. The transmission arrangement of claim 13, wherein: the first
region is designed as a first body coil arrangement having first
antenna elements arranged in parallel, with neighboring first
antenna elements being connected to one another by at least two
tuning devices; the second region is designed as two second body
coil arrangements, each second body coil arrangement having second
antenna elements arranged in parallel; neighboring second antenna
elements of the second region are connected to one another by a
connecting element; and neighboring second antenna elements of the
second region are connected to one another via at least two of the
first antenna elements of the first region.
15. The transmission arrangement of claim 3, wherein: the first
region has a plurality of first antenna elements connected to one
another via tuning devices; the tuning devices have an impedance
for the second operating frequency; a pair of second regions is
adjacent to the first region on each side of the first region such
that second antenna elements of each second region are connected to
the second antenna elements of the other second region via a first
antenna element of the first region; and the rejector circuit is
transmissive at the second operating frequency.
16. The transmission arrangement of claim 15, wherein: the first
region is designed as a first body coil arrangement having first
antenna elements arranged in parallel, with neighboring first
antenna elements being connected to one another by at least two
tuning devices; the second region is designed as two second body
coil arrangements, each second body coil arrangement having second
antenna elements arranged in parallel; neighboring second antenna
elements of the second region are connected to one another by a
connecting element; and neighboring second antenna elements of the
second region are connected to one another via at least two of the
first antenna elements of the first region.
17. The transmission arrangement of claim 2, further comprising a
plurality of input points, the plurality of input points
comprising: a first input point at the second region; a second
input point at the first region; a third input point at the second
region; and a fourth input point at the first region wherein the
first and third input points are offset by 90.degree. with respect
to one another.
18. A transmission arrangement for a tomograph, the transmission
arrangement comprising: at least one first region having first
antenna elements; and at least one second region having second
antenna elements, wherein the at least one first region and the at
least one second region are connected to one another via at least
one rejector circuit, and wherein a number of the second antenna
elements of a respective second region of the at least one second
region that are arranged parallel is less than a number of the
first antenna elements of a respective first region of the at least
one first region that are arranged parallel.
19. A transmission arrangement for a tomograph, the transmission
arrangement comprising: a rejector circuit; a first region having a
first antenna element; and a second region having a second antenna
element separated from the first antenna element by the rejector
circuit; wherein the first region and the second region are
connected to one another via the rejector circuit, and wherein the
rejector circuit is configured to prevent an operating frequency of
the first region from exciting the second region.
Description
This application claims the benefit of DE 102013205817.9, filed on
Apr. 3, 2013, which is hereby incorporated by reference in its
entirety.
BACKGROUND
The disclosed embodiments relate to a transmission arrangement for
a tomograph. The disclosed embodiments may be used in magnetic
resonance tomography, such as for the wireless energy supply of
local coil systems.
In a tomograph examination, a patient is positioned on a couch in a
cylindrical measurement area of the tomograph. A strong magnetic
field is applied in the measurement area. The magnetic field has a
gradient as a result of the excitation of a plurality of gradient
coils. The nuclear spin of atoms is aligned by the magnetic field.
Disposed within the tomograph is a transmission antenna
arrangement, such as a whole body transmission antenna arrangement,
e.g., a birdcage antenna, for emitting magnetic resonance
radio-frequency pulses to excite the atoms. The birdcage antenna is
operated with a magnetic resonance (MR) excitation frequency.
To receive the MR signals from the atoms during an MR examination,
local coils are used to receive the pulses upon the relaxation of
the nuclear spins. Different materials exhibit different relaxation
behavior. Therefore, a conclusion about the interior of the
patient's body may be drawn based on the relaxation behavior. The
local coils are often combined in assemblies (called "local coil
systems" hereinafter) and in each case have reception antenna
elements, e.g., in the form of conductor loops. The received MR
signals are also preamplified in the local coil and conducted out
of the central region of the MR installation via cables. The MR
signals are fed to a shielded receiver of an MR signal processing
device, in which the received signals are then digitized and
processed further. In many examinations, a multiplicity of local
coils are arranged on the patient to cover entire regions of the
patient's body.
The operation of MR systems is described e.g. in "Imaging Systems
for Medical Diagnostics", Arnulf Oppelt, Publicis Corporate
Publishing, ISBN 3-89578-226-2, 2006.
Energy is provided for preprocessing, such as preamplification and,
if appropriate, digitization and coding, of the MR signals in the
local coil system. The energy may be supplied via a cable, but a
cable is undesirable because the cable cannot easily be guided
(e.g., led) from the patient couch to the evaluation device. The
cable is also regarded as an annoyance by operational personnel and
by the patient. Further, the cable is fed loosely because the
patient couch is moved together with the patient and the local coil
mat.
The energy may also be supplied wirelessly via radio with a
linearly polarized energy transmission antenna in the couch and an
energy reception antenna coupled to the electronic circuit.
However, this approach involves a couch with a complex
configuration. Furthermore, the energy transmission antenna
supplies maximum power in only one position of the energy reception
antenna.
Energy is also supplied via radio with an energy transmission
antenna as an additional insert for the MR tomograph and a matching
energy reception antenna coupled to the electronic circuit.
However, this arrangement is disadvantageous because, for example,
the arrangement decreases the internal radius of the MR
tomograph.
DE 10 2011 076 918 A1 discloses a local coil system, a transmission
device, a magnetic resonance system and a method for wireless
energy transfer to a local coil system. The local coil system is
provided for an MR system for detecting MR signals with an energy
reception antenna that inductively receives energy for the local
coil system from a magnetic field that changes over time. The
energy reception antenna is tunable or tuned to an energy transfer
frequency lower than an MR excitation frequency or Larmor frequency
of the MR signals to be detected, and higher than approximately 20
kHz. The transmission device is provided for an MR system and is
configured to transmit energy to a local coil system via an energy
transmission antenna that emits a magnetic field that changes over
time and that has a predetermined energy transfer frequency. An
oscillator device is coupled to the energy transmission antenna and
generates a signal for driving the energy transmission antenna. The
signal has an energy transfer frequency lower than a Larmor
frequency of MR signals to be detected via the local coil system,
and higher than approximately 20 kHz. The energy transmission
antenna may be formed integrally with the whole body coil or around
the whole body coil. The transmission device either is relatively
voluminous or involves a complex excitation circuit.
SUMMARY AND DESCRIPTION
The scope of the present invention is defined solely by the
appended claims and is not affected to any degree by the statements
within this summary.
The present embodiments may obviate one or more of the drawbacks or
limitations in the related art. For example, the disclosed
embodiments may wirelessly provide energy into a measurement area
of a tomograph for operation of a local coil system without
reducing the internal radius of the tomograph. Wireless transfer of
energy into a measurement area of the tomograph may be achieved in
a compact manner, in which case generation of the energy transfer
signals and generation of the MR excitation signals do not mutually
influence one another, or mutually influence one another only
slightly.
A transmission arrangement for a tomograph includes at least one
first region having at least one first antenna element and at least
one second region having at least one second antenna element. The
at least one first region and the at least one second region are
connected to one another via at least one rejector circuit.
The at least one first region and the at least one second region
may be mechanically linked and, as a result, the transmission
arrangement may be constructed compactly. The at least one rejector
circuit prevents at least one operating frequency of an excited
region from exciting another region not provided for that purpose
(e.g., excitation). Any influence on the generation of the energy
transfer signal and of the MR excitation signal is suppressed.
In one embodiment, the tomograph is an MR tomograph or a nuclear
spin tomograph. However, the disclosed embodiments are not
restricted to an MR tomograph or a nuclear spin tomograph. For
example, the tomograph may be a positron emission tomograph.
In another embodiment, the antenna elements are elongate or
rod-shaped longitudinal antenna elements. The latter are well
suited to providing a homogeneous magnetic field in a cylindrical
measurement area.
In one embodiment, the rejector circuit is configured as a parallel
resonant circuit.
In one embodiment, the rejector circuit is provided for bridging a
detuning circuit (e.g., a respective detuning circuit) on the first
region. The detuning circuit may serve as an MR antenna. For this
purpose, the rejector circuit may be configured as a parallel
resonant circuit for the first region and as a series circuit for
the second region.
The rejector circuit for bridging the detuning circuit may be
configured as a parallel circuit including an inductance and a
capacitance. A capacitance is connected in series with the parallel
circuit. The capacitance may be at least one capacitor, and the
inductance may be a coil, e.g., an inductor.
The detuning circuit may correspond to the tuning device.
In another configuration, the first region is provided for
operation at a first operating frequency, the second region is
provided for operation at a second operating frequency, and the
rejector circuit is a rejector circuit for the first operating
frequency. This configuration may prevent the second region from
being excited or disturbed by the first operating frequency.
The first operating frequency may be, for example, an excitation
frequency for exciting a nuclear spin (referred to hereinafter as
an "MR excitation frequency" without restriction to other operating
frequencies). The MR excitation frequency may be, e.g., higher than
50 MHz. The at least one first region may then also be regarded as
an MR excitation antenna.
The rejector circuit for separating the regions may be configured
as a parallel circuit including an inductance and a capacitance.
The capacitance may be at least one capacitor, and the inductance
may be a coil, e.g., an inductor.
The second operating frequency may be an energy input frequency,
e.g., to supply a local coil system with energy. The energy input
frequency may be, for example, between 1 MHz and 10 MHz, such as
between 4 and 6 MHz. The at least one second region may then
constitute at least one part of an energy input frequency
antenna.
In one embodiment, the at least one first region and the at least
one second region are connected to one another via at least one
rejector circuit only for the first operating frequency. As a
result, a rejector circuit for the second operating frequency may
be obviated. The transition between a first region and a second
region is then transmissive to the second operating frequency. This
may be useful, if, for example, the excitability of the second
region by the first operating frequency is low, e.g., effectively
negligible. Also, at least part of the first region together may be
utilized with the at least one second region as an antenna for the
second operating frequency, e.g., as an energy input frequency
antenna.
In another embodiment, the detuning circuit(s) of the first region
is or are bridged via a rejector circuit (e.g., a respective
rejector circuit). The rejector circuit blocks the first operating
frequency and is transmissive to the second operating
frequency.
In another configuration, the first region has a plurality of first
antenna elements connected to one another via tuning devices. The
tuning devices have high impedance for the second operating
frequency. A second region is adjacent to the first region in each
case on both sides such that second antenna elements of the two
second regions are connected to one another via a first antenna
element of the first region. The rejector circuit is transmissive
for the second operating frequency. The tuning devices are used for
tuning the first region. This configuration is useful in that the
two second regions for the second operating frequency are linked
via the first antenna elements connected thereto and these elements
may form a single antenna. This one antenna is excited by the
second operating frequency. This enables an excitation of the
antenna and, thus, of both second regions, even when the second
operating frequency is supplied to only one of the second regions.
Moreover, as a result of the inclusion of selected first antenna
elements in this antenna, a homogeneous circular field may be
generated. The field may be generated between the two second
regions arranged on both sides. The tuning devices having high
impedance for the second operating frequency prevent, however,
other first antenna elements from also being excited via the first
excitation frequency. In this way, any influencing of the first
antenna elements by the first excitation frequency may be kept low.
Independent rejector circuits for the second operating frequency
may likewise be dispensed with in this case.
In one embodiment, the first operating frequency is always greater
than the second operating frequency. In that case, the tuning
devices may also operate as high-pass filters.
A tuning device may have, for example, a trimming or tuning
capacitor or a varactor diode or a variable capacitance diode.
In an alternative embodiment, the tuning devices between the first
antenna elements do not have high impedance for the second
operating frequency, but rather low impedance. In that case, to
prevent excitation of all of the first antenna elements by the
second operating frequency, at least one rejector circuit for the
second operating frequency is present at least between those first
antenna elements connected to a second antenna element and the
first antenna elements adjacent thereto.
In yet another configuration, the at least one first region is
configured as a first body coil arrangement having first antenna
elements arranged parallel. Neighboring first antenna elements are
connected to one another in each case by at least two tuning
devices, and the at least one second region is designed as two
second body coil arrangements having second antenna elements
arranged in parallel. Neighboring second antenna elements of a
second region are connected to one another by a connecting element,
on the one hand, and are connected to one another via at least two
first antenna elements of the first region, on the other hand. The
second region thus provides a greater field of view (FOV) for the
second excitation frequency than the first region does for the
first operating frequency. For example, in cases in which the first
operating frequency is an MR excitation frequency and the second
operating frequency is an energy input frequency, a narrow FOV of
the MR excitation field may thus be achieved. The narrow FOV may
keep a gradient ambiguity and the specific absorption rate (SAR)
low. Sufficient input of energy of local coils positioned at the
edge of the FOV of the MR excitation field may be provided (e.g.,
ensured) as a result of the greater FOV of the antenna utilized for
energy excitation and that functionally includes, for example, the
two second regions and the first antenna elements connecting the
latter.
A body coil arrangement may be an arrangement in which the antenna
elements are arranged in a ring-shaped manner. If the antenna
elements are longitudinal antenna elements, the latter may be
arranged in a cylindrical manner, such as parallel to and at an
identical distance from a central longitudinal axis. The antenna
elements may also be regarded as lying parallel to one another and
on a lateral surface of a cylinder, such as with adjacent antenna
elements being equidistant.
In another embodiment, the first and second regions may have a
cylindrical basic shape having an identical diameter. The entire
transmission arrangement may then likewise have a cylindrical basic
shape.
In one configuration, the transmission arrangement has a
cylindrical basic shape, in which the two second regions are
adjacent to the first region at end faces. As a result, a doubly
resonant transmission antenna having fields of view of different
magnitudes may be provided.
In one embodiment, the connecting element is designed at least
partly to conduct at least the second operating frequency. The
connecting element may be, e.g., a rod of the body coil
antenna.
In a configuration that suppresses the first operating frequency in
a second region to a greater extent, the connecting element is
connected to the second antenna elements via rejector circuits for
the first operating frequency.
In a configuration that suppresses the first operating frequency in
a second region to a greater extent, the connecting element between
neighboring second antenna elements has a rejector circuit for the
first operating frequency.
In one configuration, the transmission arrangement has a plurality
of input points at least including a first input point at the
second region, a second input point at the first region, a third
input point at the second region, and a fourth input point at the
first region. The input points of the respective region are offset
by 90.degree. with respect to one another, e.g., the first input
point and the second input point, and the third input point and the
fourth input point.
An offset arrangement may be an arrangement angularly offset by a
longitudinal extent in a circumferential direction.
In one configuration, the first input point and the third input
point are disposed between at least one (e.g., two) second antenna
elements of the second region.
In one embodiment, the second and fourth input points are disposed
between at least one (e.g., two) first antenna elements (e.g.,
longitudinal antenna elements) of the second region.
In one embodiment, the second and fourth input points are disposed
opposite the first input point and third input point, respectively,
and are not angularly offset with respect to one another.
In one embodiment, the second and fourth input points are not
disposed opposite the first and third input points, respectively,
and are angularly offset with respect to one another.
In another configuration, the number of second antenna elements of
a second region that are arranged in parallel is less than the
number of first antenna elements of a first region that are
arranged in parallel. However, the number of antenna elements may
also be identical. Furthermore, the number of second antenna
elements of a second region that are arranged in parallel is
greater than the number of first antenna elements of a first region
that are arranged in parallel.
In accordance with another aspect, a tomograph, such as an MR
tomograph, includes at least one such transmission arrangement.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a transmission arrangement for an MR tomograph in
accordance with one embodiment.
DETAILED DESCRIPTION
FIG. 1 shows a transmission arrangement 101 for a magnetic
resonance tomograph T. The transmission arrangement may also be
configured as a transmission antenna. The transmission arrangement
101 includes three regions, namely, a central first region 102
having a cylindrical basic shape and, adjacent thereto at the end
sides, a second region 103 and a second region 104. The two second
regions 103, 104 are likewise of cylindrical basic shape and of the
same diameter as the first region 102. As a result, the
transmission antenna 101 as a whole also has a cylindrical shape.
The longitudinal axis of the cylindrical shape corresponds to the
z-axis z. The two second regions 103, 104 have a construction that
is mirror-symmetrical with respect to the longitudinal axis z.
The first region 102 has thirty-two linear or rod-shaped antenna
elements, which are designated hereinafter as first longitudinal
antenna elements 105. The first longitudinal antenna elements 105
are aligned in parallel to one another and in parallel to the
longitudinal axis z. The first longitudinal antenna elements 105
may be angularly offset equidistantly in the circumferential
direction about the longitudinal axis z and are therefore at the
same distance from the longitudinal axis z. This arrangement of the
first longitudinal antenna elements may also be designated as a
"body coil arrangement" or a "birdcage arrangement".
The first longitudinal antenna elements 105 have connection regions
106 widened at both ends. Adjacent first longitudinal antenna
elements 105 are connected to one another at the connection regions
106 thereof via tuning devices, e.g., in the form of a tuning
capacitor 107.
The two second regions 103 and 104 have eight linear or rod-shaped
antenna elements, which are designated hereinafter as second
longitudinal antenna elements 108. The second longitudinal antenna
elements 108 are also aligned in parallel to one another and in
parallel to the longitudinal axis z. The second longitudinal
antenna elements 108 are likewise angularly offset equidistantly in
the circumferential direction about the longitudinal axis z and are
therefore at the same distance from the longitudinal axis z. The
regions 102, 103 and 104 have the same diameter such that the first
longitudinal antenna elements 105 and the second longitudinal
antenna elements 108 are at the same distance from the longitudinal
axis z. This arrangement of the second longitudinal antenna
elements likewise corresponds to a "body coil arrangement" or a
"birdcage arrangement".
Second longitudinal antenna elements 108 of the second regions 103
and 104 are disposed opposite relative to one another along the
longitudinal axis z. The second longitudinal antenna elements 108
therefore lie along an identical axis parallel to the longitudinal
axis z. The second longitudinal antenna elements 108 are connected
to one another by a first longitudinal antenna element 105, 105a in
each case. This connection is not established directly, but rather
via respective rejector circuits 109 between the second
longitudinal antenna elements 108 and the first longitudinal
antenna element 105, 105a connected thereto.
At the end of the longitudinal antenna elements 108 opposite to the
first longitudinal antenna element 105, 105a, the second
longitudinal antenna elements 108 of the second regions 103, 104
are connected to one another via a respective end ring 110.
The tuning capacitors 107 are configured such that the capacitors
107 have high impedance for a second operating frequency of the
second regions 103 and 104 (referred to hereinafter as an "energy
input frequency"). The tuning capacitors 107 thereby prevent the
energy input frequency from being fed or input into the first
longitudinal antenna elements 105, 105b not connected to the second
longitudinal antenna elements 108, or prevent such input at least
to a practically small or negligible extent.
The rejector circuits 109, by contrast, block a first operating
frequency of the first region 102 (referred to hereinafter as an
"MR excitation frequency"), such that the MR excitation frequency
is not fed or input into the second longitudinal antenna elements
108, or is fed in only to a practically negligible extent. The
rejector circuits 109 may be configured as parallel resonance
circuits. The rejector circuits 109 may be provided for bridging a
detuning circuit (not illustrated), e.g., a respective detuning
circuit, at the first region 102.
Overall, this results in a doubly resonant transmission arrangement
101 in a body coil arrangement. The first region 102 may be
operated with the MR frequency, e.g., in order to excite bodies
disposed in the first region 102 to undergo nuclear spin resonance.
By contrast, the second regions 103 and 104 are not influenced, or
not significantly influenced, by the MR excitation operation of the
first region 102.
The second regions 103 and 104 connected to one another via the
first longitudinal antenna elements 105a are used, by contrast, for
wirelessly feeding energy into local coils or local coil systems
(as described, e.g., in DE 10 2011 076 918 A1). The second regions
103 and 104 together with the first longitudinal antenna elements
105a may therefore form an energy input antenna 103, 104, 105a in
body coil or birdcage form, which may be operated at the energy
input frequency. The energy input frequency is lower than the MR
excitation frequency and, in this example, is between 1 MHz and 10
MHz. By contrast, the MR frequency in this example is higher than
50 MHz.
The end rings 110 of the second regions 103 and 104 may be
connected to the associated second antenna elements 108 via
additional rejector circuits 114 for the MR excitation frequency to
further reduce the interference effect of the MR excitation
frequency on the energy input antenna 103, 104, 105a.
The end rings 110 in this example have a plurality of
ring-sector-shaped portions 115. The portions 115 are connected to
one another by rejector circuits 116 for the MR excitation
frequency in such a way that adjacent second antenna elements 108
are connected to one another via a respective rejector circuit 116.
The end ring 110 has a rejector circuit 116 for the MR excitation
frequency between adjacent second antenna elements 108.
The energy input antenna 103, 104, 105a is useful in that the
energy input frequency need be fed in or input at only one of the
second regions 103 or 104. This is indicated in this example by a
first input point 111 and a third input point 113 at the end ring
110 of the first region 103. The third input point 113 is disposed
in a manner angularly offset by 90.degree. about the longitudinal
axis z with respect to the first input point 111. As a result, the
first input point 111 and the third input point 113 are separated
from one another by two ring-sector-shaped portions 115 of the
common end ring 110. The energy input antenna 103, 104, 105a may be
operated by the energy input frequency being applied to the first
input point 111 and the third input point 113.
A second input point 112 and a fourth input point 114 are disposed
between two respective first longitudinal antenna elements 105b of
the first region 102. The second input point 112 and the fourth
input point 114 are disposed opposite the first input point 111 and
the third input point 113, respectively, relative to the
longitudinal axis z. The second input point 112 and the fourth
input point 114 are therefore likewise angularly offset by
90.degree. about the longitudinal axis z. The first region 102,
serving as MR antenna, may be operated by the MR excitation
frequency being applied to the second input point 112 and the
fourth input point 117.
Since the rejector circuits 109 are configured to block the MR
excitation frequency, but not the energy input frequency,
corresponding excitation currents also flow through the first
longitudinal antenna elements 105a and through the opposite second
region 104. On the other hand, however, because the tuning
capacitors 107 are configured to have high impedance for the energy
input frequency, the other longitudinal antenna elements 105b are
not excited, or not significantly excited, by the energy input
frequency. The first region 102 is therefore effectively decoupled
from the energy input frequency without requiring dedicated
rejector circuits for that purpose. Therefore, the first region 102
may effectively serve as an MR antenna for emitting excitation
signals for generating nuclear spin excitations without
interference by the energy input frequency.
The transmission arrangement 101 may also be useful in that the
first region 102 serving as an MR antenna has a comparatively
narrow FOV, which keeps signal ambiguities (e.g., relative to a
gradient) and the SAR low. By contrast, the energy input antenna
103, 104, 105a has a wider FOV, through which local coils
positioned at an edge of the FOV of the first region 102 may be
reliably supplied with energy. Such marginally positioned local
coils may also be operated by a homogeneously present energy input
field.
It is to be understood that the elements and features recited in
the appended claims may be combined in different ways to produce
new claims that likewise fall within the scope of the present
invention. Thus, whereas the dependent claims appended below depend
from only a single independent or dependent claim, it is to be
understood that these dependent claims can, alternatively, be made
to depend in the alternative from any preceding or following claim,
whether independent or dependent, and that such new combinations
are to be understood as forming a part of the present
specification.
While the present invention has been described above by reference
to various embodiments, it should be understood that many changes
and modifications can be made to the described embodiments. It is
therefore intended that the foregoing description be regarded as
illustrative rather than limiting, and that it be understood that
all equivalents and/or combinations of embodiments are intended to
be included in this description.
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